Devices for the application of developer powder



Feb. 8, 1966 G cRANSKE-Ns ETAL 3,233,586

DEVICES FOR THE APPLICATION OF DEVELOPER POWDER 2 Sheets-Sheet 1 Filed July 20, 1962 AWE/V7025 GEORG CRAN SKENS UWE T HURAT AGENT Feb. 8, 1966 CRANSKENS' ETAL 3,233,586

DEVICES FOR THE APPLICATION OF DEVELOPER POWDER 2 Sheets-Sheet 2 Filed July 20, 1962 kNA n0 mmm WR w 4 0 3 v:

AGENT United States Patent 3,233,586 DEVICES FOR THE AEPPHCATHQN 0F DEVELQPER FUWDER Georg Qranshens, Wedei in Holstein, and Uwe Thurat, Hamburg, Germany, assignors to Lurnoprint Zindler Kt Hamburg, Germany Filed .i'uiy 24), W62, Ser. No. 211,364 Claims priority, appiication Germany, .lluly 2'7, 1961, I. 393642 5 Ciaims. (El. 118-637) The invention relates to a device for applying developer powder to a sheet of exposed electrophotographic material by using a rotating magnet roller and a container with developer powder into which the roller clips for building a 'brushdike array or wad of particles on the periphery of the roller.

In the use of such magnetic rollers it is usual to guide the copy material along a defined support laterally of or underneath that roller, whereby the wad of developer powder is compacted and greatly deformed. Further developer powder is then deposited on this compressed mass so that eventually there exists a comparatively hard powder layer which exerts considerable friction on the copy material. Consequently, there is the danger that developer particles rub into the surface of the paper so that an unclear image or blurred outlines are produced.

It is also known to draw the copy material over a developer-powder pile by means of a fixed drum, the drum having a section dripping into this pile. Considerable frictional etlects also arise in this case. If the developer powder is applied to the drurn-supported copy sheet by means of several magnetic rollers dipping into the pile, strong friction again exists and the developer powder applied by the first roller is considerably distorted particularly by the brushing action of the last roller.

The invention aims at improving prior powder distributors of the magnetic-roller type thereby providing a construction which not only provides a more loose and elastic developer-powder wad but also ensures mixing of the developer powder in the apparatus. This problem is solved according to the invention by the provision of at least one stripper for the loosening of the wad, preferably substantially in the vicinity or ahead of the circumferential region at which the rotating magnetic roller dips into the developer-powder sup-ply. Advantageously, a comb-like further stripper provided within the developer-powder pile is disposed on the ascending side of the roller near the point of its emergence from the pile, the latter stripper consisting essentially of individual bars which extend substantially radially of the roller.

According to a preferred embodiment the first stripper, arranged on the descending side of the magnetic roller, is a blade of rigid material extending substantially tangentially of the roller and terminating for example at a small distance therefrom.

According to a special construction this blade is shaped helically for simultaneous lateral displacement of the developer powder axially of the roller. In this way a particularly good disintegration is obtained, the developer powder being alternately released from the magnetic roller and applied thereto.

Advantageously the blade is formed with a symmetrically helical twist from the middle of the magnetic roller to both ends. There is thus produced, according to the pitch direction of the screw thread, an outward displacfiment from the center, which is preferred for situations in which the developer powder is replenished by feeding fresh powder into the central region, or an inward displacement from the ends.

According to a particularly advantageous embodiment, about its longitudinal axis and can be driven in order the helical blade forming the first stripper is rotatable to transport the developer powder axially of the roller, to stir the developer powder and to supply it to the lower peripheral section of the roller.

Avantageously, the magnetic roller is constructed so that peripheral sections extending parallel to the axis and spaced from one another form alternate north and south poles. Although the invent-ion also includes other contructions of magnetic rollers, the above-mentioned construction is particularly suitable in association with a stripper according to the invention since the combination of such a roller with a stripper causes a steady loosening of the powder wad whose particles are thus uniformly distributed over the whole length of the roller.

The invention further relates to a particularly advantageous type of developer powder as supply for such a device. This developer powder is briquetted in the form of a rod which can be progressively pulverized, being thus available for use as a shaped body.

Further advantages and features of the invention will be evident from the following description of the specific embodiments illustrated in the accompanying drawing, in which:

FIG. 1 shows a sectional side view of a device for applying developer powder in accordance with the invention;

FIG. 1a is a face view of a stripper forming part of the device of FIG. 1;

FIG. 2 shows a side view of a further embodiment of the invention with the supply container shown in section;

FIG. 3 shows a view taken in section along the line III-III in FIG. 2;

FIG. 4 shows a sectional side view of a still further embodiment;

FIG. 5 shows a partial sectional side view of yet another embodiment;

FIG. 6 shows a partial sectional side view of still another embodiment; and

FIG. 7 shows a sectional side view of yet a further embodiment.

In the drawing only the parts essential for an understanding of the invention are shown, auxiliary elements being shown schematically in order not to obscure the views.

In all figures, a magnetic roller is indicatedby reference numeral 1, a container for the developer powder by reference numeral 2, a developerapowder supply in the container :by reference numeral 3, and a brushlike powder formation or wad roller by reference numeral 4. The magnetic roller has a shaft 5, supported in side walls of the supply container, which extends through at least one side thereof and is connected with a drive mechanism 6.

Rotation is effected for example in the direction of the arrow '7, i.e. counterclockwise in FIG. 1.

The roller 1 is preferably constructed as a smooth annular magnet. Thus only a small moment is required for stripping the wad of developer powder and a simple construction of the magnet is made possible. The magnetization is effected, for example, in the peripheral direction with alternate north and south poles, the roller being provided for example with four to six or eight poles, six pole pairs being shown in FIG. 1 with, for example, intervening layers of non-magnetic material as is conventional.

The container 2 has at one side guide means 8, 9 for admitting a copy sheet. These guide means are disposed so that the sheet is supplied to the upper side of the roller whereby particles entrained by the roller are caused to adhere to the underside of the sheet to develop a latent image thereon. On the opposite side further guide means it), 11. are arranged, of which the lower guide means 16 is constructed a pin wheel in order not to damage the developed powder image. Before the guide surfaces 3 and 9, for example, drive or transport rollers can be provided, yet the guide means and 11, which are both wheels or rollers and of which at least the wheel is constructed as a :pin wheel, can act as drive elements. it will be noted that the level of a sheet guided through the container 2, as determined by the surfaces 3, 9 and the rollers 10, 11, is above the magnetic roller 1 and substantially tangent to the cylindrical wad 4 of magnetic particles entrained thereby.

As shown in FIG. 1, a bladeehaped stripper 12 is provided whose beveled edge 13 is directed tangentially of the periphery of the roller 1 at t.e position at which the roller, for the direction of rotation indicated, enters the developer-powder supply. Consequently, the wad 4, which is compacted under pressure against the copy material in the upper region of the roller, is detached from the roll- The blade edge 13 is preferably arranged in the immediate vicinity of the surface of the magnetic roller so that in practice a complete removal of the developer powder takes place. However, even when there is a small spacing between the edge 13 and the magnetic roller, the rest of the developer powder remaining on the roller on account of this spacing can be disintegrated behind the stripper 12 and newly formed.

The stripper 12 preferably comprises non-magnetic, for example, plastic, material. In addition, as shown in FIG. 1, a further stripper 14 in the shape of a comb or rake (see FIG. 1a) is arranged within the developer-powder pile 3 and ahead of the position at which the periphery of the magnetic roller leaves the pile, which effects a further loosening of the wad 4 bfore the latter emerges from the supply pile.

As shown in FIGS. 2 and 3 the stripper 15, whose positioning corresponds substantially to that of the stationary stripper 12 (FIG. 1), is shaped so that at its central region it forms a trough which is open upwardly and towards the roller 1 and whose mouth is flared out towards the ends ofthe roller. For this purpose the stripper blade 15 is given a helicoidal twist in the same direction on opposite sides of the center line 16.

This embodiment has the advantage that the developer powder of the wad stripped from the roller surface is displaced laterally outwardly to the ends of the roller, whereby a mixing effect is obtained. The stripper 15 is for example rotatable on stub shafts 1'7, 18 supported in the side walls 53, 34 of the container 2 and is either selectively rotatable by means of a hand crank Z-t, for example for the establishment of special conditions of disengagement or for the distribution of supplemental developer powder supplied in the region, e.g. as illustrated at in FIG. 2 or is coupled to the drive mechanism 6 for the roller by connection of a reduction gearing or a transmission 19 with the stub shaft 18. The bearings are only schematically illustrated and are preferably constructed to talre up axial forces.

It only a hand drive mechanism 24 is provided, a ratchet device or friction brake 20 is provided for example on the stub shaft 17 to enable fixing in a selected position.

FIG. 3 clarifies the arrangement shown in FIG. 2 to make it apparent that in the region of the median horizontal plane of the roller, ie at 21, developer powder is scraped off the wad and can be transported downwardly and outwardly, while outer sections of the wad are stripped and travel on the stripper 15 on the outer side thereof to the vicinity of the center line 1 6, thus resulting in a thorough agitation of the powder mass.

In FIG. 4, a screw-shaped stripper 22 is provided in lieu of the aforedescribed members 12 and 15. With the stripper at rest there would occur, according to the selected pitch direction of the screw thread, a shifting of the powder mass to one side of the supply container. This stripper is connected by its stub shaft 18 and the transmission l'ft to the drive mechanism 6 for rotation in such a sense and at such a rate, depending on the magnitude of the selected pitch of the stripper, that this unidirectional shift does not talze place and only a SCI: p ng and mixing of the developer powder with simultaneous detachment of the wad from the roller is accomplished. The embodiment illustrated has the advantage that the positions at which the wad is released in t' e immediate vicinity of the roller periphery constantly change in accordance with the rate of rotation of the helical stripper 23.

FIG. 5 shows an alternative embodiment having a stripper 23 which has a helical twist extending symmetri- Cally outwardly from the center line 16. With the stripper held stationary there is produced, according to the selected thread, a rolling from the center outwardly or from the ends inwardly. This embodiment has particular advantages it for fresh developer powder is s ppiicd in the central region. This additional powder is then gradually displaced outwardly.

If the strippe- 23 is driven by hand or via a transmission 19, the effect of a lateral rolling can be produced and, in the above-described manner, the disintegration and detachment 0f the powder wad by lateral displacement of the mass in the immediate vicinity of the magnetic roller can be varied.

FIG. 6 shows a modification of the embodiment shown in FIG. 5 wherein a stripper 27 is provided, on each side of its center line 1 5, with only a single helical turn, the pitch of this twist varying so th.t the middle sections 25, are elongated with respect to the outer sections 26,

The embodiments according to FIGS. 2, 4, 5 and 6,

in particular, enable fresh developer powder, briquetted for example in red shape, to be introduced in the axial direction of the roller 1 between the latter and the stripper 15, 22, 23 or 27, this briquetted rod 320, FIG. 3, being pulverized by the illustrated stripper. A further embodiment of the invention provides for the positioning of a more loosely briquetted supply rod of developer powder past which the wad i rotates, preferably before it passes the first stripper, so as to entrain particles of developer powder from that rod. The arrangement of such a rod is schematically shown for example in FIG. 1. As shown in this figure, a holding tray 31 on the container 2 supports a rod 32 of developer powder so that the wad 4 contacts the rod 32 before it arrives at the stripper 12. Consequently, the supply is constantly replenished with developer powder in accordance with the cohesiveness of the briquette. The degree of cohesion necessary to ensure a uniform supply rate of developer powder in the container 2 can be determined by experiment.

The rod 32 can be arranged in a manner other than in the trough-like holder illustrated. If the holder 31 is used, at least the lower part thereof is in the form of fingers extending perpendicularly to the axis of the magnetic roller in order to avoid stripping the wad 4- when the latter reaches the lower edge of the holder 31.

A construction of this type enables a simple renewal of the developer-powder supply and a more dust-free operation than in prior systems wherein a loose mass of developer powder had to be distributed.

FIG. 7 shows a special embodiment of a stationary blade-shaped stripper 23 which can replace the stripper 12 in FIG. 1. This stripper is formed with an indulating upper edge 29, 3%) so that adjacent zones of the powder wad are stripped from the roller or redistributed laterally in axial direction of the roller according to whether a crest-like edge portion 29 projecting towards the roller or an indented edge portion 30 spaced from the roller confronts the particular peripheral section of the roller.

A common feature of the strippers 15, 22, 23, 27 and 28, as clearly seen in FIGS. 2 and 4-7, is their undulating profile in vertical projection, its shape being such that the stripper approaches close to the roller surface at axially spaced locations which are either fixed (FIG. 7) or changing (FIGS. 2-6).

We claim:

1. A device for distributing developer powder over a surface of a sheet of exposed electrophotographic material, comprising a container provided with substantially horizontal guide means for the passage of said sheet therethrough; a cylindrical roller in said container disposed for rotation about a horizontal axis below said guide means, said container forming a receptacle for a pile of developer powder rising above the lower roller surface, said roller being magnetized along its surface with alternating north and south poles for entraining a wad of particles from said pile across the underside of said sheet whereby some of said particles adhere to said sheet for developing a latent image thereon, and a helicoidally twisted stripper blade extending substantially horizontally close to the periphery of said roller along its descending side for disengaging said wad from the roller surface upon re-entry into said pile.

2. A device as defined in claim 1 wherein said blade is rotatably journaled in said container, further comprising drive means for rotating said blade about a horizontal axis parallel to that of said roller.

3. A device as defined in claim 1 wherein said blade is twisted with symmetrical pitch on opposite sides of a vertical median line.

4. A device as defined in claim 3 wherein said blade is rotatab-ly journaled in said container, further compris ing drive means coupled with said blade and said rotor for rotating same in synchronism about parallel horizontal axes.

5. A device as defined in claim 3 wherein said blade is rotatable by said drive means in a direction causing the spread of said powder horizontally outwardly from said median line, further comprising supply means for deliver-ing fresh powder to said container in the region of said median line.

References Cited by the Examiner UNITED STATES PATENTS 1,101,200 6/1914 Leister et al. 156-453 1,729,811 10/ 1929 Anderson 118-204 1,956,561 5/1934 Coates 118-126 2,786,440 3/1957 Giaimo 118-637 2,974,632 3/1961 Westervelt et al. 118-637 X 3,002,434 10/ 1961 Reuter 118-637 X 3,003,462 10/ 196 1 Streich 118-637 3,081,737 3/1963 Frantz et al. 118-637 3,098,765 7/ 1963 Keller et al 118-637 3,152,924 10/ 1964 Wanielista et al. 118-637 CHARLES A. WILLMUTH, Primary Examiner.

WILLIAM D. MARTIN, Examiner. 

1. A DEVICE FOR DISTRIBUTING DEVELOPER POWDER OVER A SURFACE OF A SHEET OF EXPOSED ELECTROPHOTOGRAPHIC MATERIAL, COMPRISING A CONTAINER PROVIDED WITH SUBSTANTIALLY HORIZONTAL GUIDE MEANS FOR THE PASSAGE OF SAID SHEET THERETHROUGH; A CYLINDRICAL ROLLER IN SAID CONTAINER DISPOSED FOR ROTATION ABOUT A HORIZONTAL AXIS BELOW SAID GUIDE MEANS, SAID CONTAINER FORMING A RECEPTACLE FOR A PILE OF DEVELOPER POWDER RISING ABOVE THE LOWER ROLLER SURFACE, SAID ROLLER BEING MAGNETIZED ALONG ITS SURFACE WITH ALTERNATING NORTH AND SOUTH POLES FOR ENTRAINING A 